High Low Method Question

Hi Sir,

I am using the BPP revision kit for BPP and am confused by the high-low method when there is a highest total output is not the highest total cost . How would i proceed?

i.e.

A company, which manufactures a range of products, has decided to introduce a product costing system. As a first step it wishes to analyse the behaviour of its costs.

The following data is available for the previous four periods

Total Costs 214,559 239970 243,183 259,541
Total Output 64,200 79,350 86,170 85,620

a) Using the high-low method, which ONE of the following formulae will correctly calculate the cost of the variable element per unit?

(it then goes onto to listing four options)

—–

My answer was to do (243183-214559)/(86170-64200). I did this because I was under the assumption that we always use the highest units, not the highest costs, when there is a discrepancy of this sort.

The actual answer as provided in the book is 259541-214559/85620-642000. They used the highest total cost as the determinant.

It would be very helpful if you could advise on the matter. Which one should I use?

Thanks,
Yazan